JPS6267495A - Cooling system on isolation of nuclear reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a method for supplying cooling water to reactor C to maintain the reactor water level when the injection of cooling water from the water supply system stops after a reactor scram. Reactor isolation cooling system

[Technical Background of the Invention] Generally, a reactor isolation cooling system for a conventional boiling water nuclear power plant is configured as shown in FIG. 2C.

Here, Figure 2 shows a conventional boiling water nuclear power generation blunt C:
A schematic configuration diagram of such a reactor isolation cooling system is shown. Figure 2C
In the reactor containment vessel 1, a reactor pressure vessel 3 containing a reactor core 2 therein is housed, and a suppression pool 4 is formed below the reactor containment vessel 1. The steam generated within the reactor pressure vessel 3 is led to the main turbine 6 via the main steam pipe 5. The main turbine 6 is rotated by the guided steam C, and a generator 7 connected to the main turbine 6 is driven.

The steam supplied to the rotating section of the main turbine 6 becomes condensate in the condenser 8 (condensed water). I get run over.

In the above configuration C:, if the feed water pump 9 stops for some reason during power operation, the reactor water level will decrease, but the reactor water level will not fall below a certain fixed value. The reactor is scrammed and the reactor is shut down.

Even if the reactor is shut down, the water level in the reactor continues to fall as steam continues to be generated from decay heat. In such a case, 1
A reactor isolation cooling system (hereinafter abbreviated as RCIC) is installed, and when the reactor water level falls below a certain water level, the RCIC turbine 11 is likely to be driven by reactor steam (both pumps 12 is driven, condensate storage tank 1
3 or suppression boule 4 is injected into the reactor pressure vessel 3 to maintain the reactor water level.

The water injection flow rate by the RCICC is controlled at a constant flow rate by controlling the speed of the pump 11 by a signal from an IC flow regulator (not shown). By changing the setting value, the water injection flow rate can be adjusted.

[Problems with Background Art] In recent efforts to improve boiling water reactors, there is no design that incorporates ζ-RCIC in the emergency core cooling system (hereinafter referred to as GEES). This ECC8 automatically activates in the event that a pipe connected to the reactor pressure vessel ruptures (hereinafter referred to as LOCA), or if a drop in the reactor water level or a rise in pressure in the reactor containment vessel is detected. , has the function of injecting cooling water into the reactor pressure vessel and preventing or suppressing major damage to the fuel tubes housed in the reactor core.

Now, if RCIC is incorporated as part of ECC8 (U), RCl can adjust the water injection flow rate manually (as shown above), so there is no possibility that the operator may accidentally reduce the water injection flow rate during LOCA. There is a risk that this may occur.

This ECC8 is designed so that the safety function can be achieved even if one system fails, so a decrease in the water injection flow rate of the RCIC does not mean that it will directly lead to fuel failure.

However, being able to manually change the water injection flow rate during LOCA (URCIC) is not desirable from a safety standpoint.

[Object of the invention] The present invention provides an RCI that operates as ECC8 during LOCA.
The purpose of the present invention is to obtain an RCIC that can maintain the operating rating even if an operator makes a malfunction when the RCIC is activated during LOCA.

[Summary of the Invention] The present invention injects cooling water into the reactor when water supply is stopped after a reactor scram, and injects cooling water into the reactor during a loss of coolant accident (inside the reactor (inside the reactor). The reactor isolation cooling system is characterized by being equipped with a flow control prohibition circuit that prohibits control of the water injection flow rate by manual control for a certain period of time after a coolant loss accident occurs. .

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIG. Here, FIG. 1C shows a schematic configuration diagram of a cooling string during nuclear reactor isolation according to an embodiment of the present invention. In FIG. 1C, parts that are the same as those in FIG. 2 are designated by the same reference numerals, and the explanation of the structure of those parts will be omitted. In FIG. 1, a part of the steam led from the main steam pipe 5 is led to the RCIC turbine 11 via the pipe L4. This pipe 14 has an RCIC
Steam control valve 1 that controls steam guided to the turbine 11
5 is provided. This steam control valve 15 is operated by a signal output from the RCIC flow controller 16. The flow rate is regulated by the RCI C flow controller 16 and the manual controls 1 and 8 via the toggle switch 17. ] Normally, the switch 17 is set to the A side in Fig. 1, but when LOCA occurs, the reactor water level low signal 19
Alternatively, when the containment vessel pressure cylinder signal 20 is output, the switch 17 is switched to the B side. A timer 21 is provided on the B side, and this timer 21 starts when the reactor water level low signal 19 or the containment vessel pressure high signal 20 is output, and the timer 21 starts when the reactor water level low signal 19 or the containment vessel pressure high signal 20 is output. The control signal 18 is configured so that the RCI (:#) amount regulator L is not manually operated.The time set in the timer 21 is usually about 10 minutes (the time for the maximum LOCA to converge). : Set.

According to the above configuration, even if a LOCA occurs and the operator manually incorrectly controls the flow rate, the control signal will not be activated. The water level in the reactor can be maintained at a predetermined constant value (2), and water injection into the reactor by the RCIC is performed normally, so the water level in the reactor can be maintained.

[Effect of the invention] As shown above, the invention
#l.

In RCICζU with 48 abilities of GEES
For a certain period of time after CA occurs, the rated flow rate of the RCI (, : can be ensured (2)) to ensure automatic control so that the RCIC does not flow (2) even if the worker malfunctions the RCIC. .

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a cooling system for reactor isolation according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of a conventional cooling system for reactor isolation. 11...Reactor isolation cooling system (RCIC) turbine]
2... Pump 13... Condensate storage tank 1
5...Steam control valve 16...Reactor isolation cooling system (RCIC) flow regulator 17...Switch 18...Manual control signal 1
9...Reactor water level low signal 20...Containment vessel pressure high signal 21...Timer agent Patent attorney Noriyoshi Chika Yudo Hirofumi Mitsumata Figure 2

Claims (3)

[Claims] (1) In a reactor isolation cooling system that injects cooling water into the reactor when the water supply is stopped after a reactor scram, and injects cooling water into the reactor in the event of a loss of coolant accident,
A reactor isolation cooling system comprising a flow rate control prohibition circuit that prohibits manual water injection flow rate control for a certain period of time after a loss of coolant accident occurs. (2) The flow rate control prohibition circuit is activated by a loss of coolant accident signal, and is configured so that the water injection flow rate manual control signal is not input to the flow rate regulator installed in the reactor isolation cooling system within a certain period of time after activation. A nuclear reactor isolation cooling system according to claim 1, characterized in that the cooling system comprises: (3) Reactor isolation according to claim 1, wherein the certain period of time during which control of the water injection flow rate is prohibited is set to 10 minutes, which is the time during which the maximum coolant loss accident is resolved. time cooling system.